In recent years, evidence has been accumulating for the serious detrimental impact of childhood trauma exposure on child and adult physical and mental health. This evidence is mostly based on retrospective studies of traumatized adults. Prospective longitudinal studies in children are necessary to determine the impacts of trauma on neurobiological development. Furthermore, effects of trauma are not static, and may oscillate based on environmental factors affecting neurobiology of traumatic stress. Examining the longitudinal course in trauma-related symptoms in children will help in identification of biological and environmental factors contributing to vulnerability and resilience. While parental and environmental factors have an impact on stress in traumatized populations, the biological mechanisms of this transmission are not yet clear. Exploring these factors is vital in determination of the most important modifiable factors affecting childhood mental health following trauma exposure in order to inform future interventions. We will leverage an existing cohort of Syrian and Iraqi refugee children ages 7-17 and their parents who settled in the United States starting in 2016. We will explore longitudinal changes in symptoms of anxiety, depression, and posttraumatic stress disorder (PTSD) post war-zone trauma in Syria, as well as resettlement, and their epigenetic, autonomic, and environmental correlates. We have already established the impact of exposure to war trauma and stress of migration in this cohort and their parents within one month of their arrival in the United States. This initial assessment (Wave 1) showed high rates of anxiety in the children, and high rates of PTSD and anxiety in their parents. We propose to follow this cohort (Wave 2, 12-24 months, and Wave 3, 24- 36 months), with collection of self-report measures of anxiety, depression and PTSD, saliva DNA samples, and skin conductance response as peripheral marker of sympathetic arousal. [We will also do a cross sectional comparison of above symptoms and biomarkers with Arab immigrant children without war trauma exposure]. This proposal represents the first study to examine course of illness, epigenetic, autonomic, and environmental correlates of stress and trauma among Syrian refugee children and their parents. A strength of the study is the known developmental timing of trauma exposure and availability of assessments immediately upon arrival, as well as the ability to follow-up the children longitudinally during development. The possibility of finding potential unique epigenetic changes, as well as most important environmental and parenting risk factors, promises to advance efforts to improve child outcomes and reduce risk for later mental and physical health problems associated with childhood trauma and stress. This knowledge will not only be useful in providing better health services to this specific population in need, but also in increasing our more general understanding of trauma and environmental impact on child development and psychopathology.